Sparking plug



Feb. 2, 1943. F R,y F- HAMSAY 369,98?

SPARKING PLUG Filed March 5, 1941 Paienfe'd Feb. 2, 1943 SPARKING PLUG Frank Raymond Faber Ramsay, London, England, assignor to D. Napier 8: Son Limited, London, England, a company of Great Britain Application March 5, 1941, seria@ No. 381,910

In Great Britain March 13` 1949 9 Claims.

This invention relates to sparking plugs for inernal combustion engines, and an object of the -nvention is to provide a sparking plug adapted more particularlyI for use with high duty air-r craft and like engines. I

A sparking plug includes a bush insulator mounted in a hollow metal body which in turn is mounted in the cylinder head. The gland by which the insulator is ilxed in the body not only provides a gas-tight seal but also affords a path for escape of heat from the insulator to the body and thence to the cooled parts of the cylinder head.

The inner end of the insulator which bears the sparking point is spaced from the body for a certain length and this space is known as the gas space, the length of insulator exposed and the space around it being varied according to the degree of insulation required and the maximum temperature allowable.

In customary constructions the portion of the 'body surrounding the gas space is of reduced diameter and carries the screw-thread by which the plug is held in the cylinder head. This limits the extent to which the screwthread can be prolonged towards the gland since it would either unduly weaken the body wall or would actually be too small to accommodate the gland. Hence g the heat from the insulator has to take a comparatively long and oircuitous path not only iiowing up-the insulator to the gland but also flowing down the body from the gland to the screwthread before reaching the cylinder head.

According to this invention the part of the plug body which is externally screwthreaded to engage the threaded hole in the cylinder head has the same external diameter as the adjacent part of the body within which lies the gland. This external screwthread extends over at least some o! that part of the body within which lies the gland. Thus at least a part of the gland through which 'neat can flow radially from the insulator to the body lies within a part of the body which, since it is screwthreaded and engages the hole in the cylinder head, provides means for the heat to flow radially and substantially directly from the insulator to the cylinder head. That end portion of the body which extends beyond the externally screwthreaded part and within which lies at least a part of the gas space has a diameter less than that of the adjacent screwthreaded part of the body. 'Ihis permits a reduction to be made in the size of the hole which must be provided in the cylinder head and consequently in the hot spot which results from this Preferably the end portion of the body is tapered to engage a correspondingly tapered or conical seating within the hole in the cylinder head. By reason of the above-described construction it is possible for that part of the body which is cf uniform diameter to be oi' such substantial length between the end of that part and the usual external hexagonal formation that it may be at least three times the length of its end portion along which runs the screwthread.

By placing the screwthread around or close to the gland the prolongation of the body becomes merely the means of enclosing the gas space and carrying the earth electrodes and is freed from the duty of holding the plug in the cylinder head. This is a further advantage since with small diameter sparking plugs it is not always easy to provide a screwthread sufliciently strong for this purpose with a diameter of the size permitted at the end.

The tapered surface at the end of the body affords a gas seal and gives good cooling for the earth electrodes of the sparking plug.

The accompanying drawing shows by way of example a construction of the improved sparking plug, the view being half in elevation and half in longitudinal section.

The insulator A is of ordinary construction and is permanently secured in the body B of the plug by means of a gland which comprises a seatink washer C, a gland ring D and a retaining ring E which is spun in place in a known manner. Surrounding the gland the outer surface B1 of the body of the plug is substantially cylindrical and this cylindrical part extends to a point which lies outside of and about half-way along the gas space F. From this place to a point which is approximately on a level with the Junction `.3e-tween the seating washer C and the gland ring D this cylindrical surface is screwthreaded as at IB2 to engage the correspondingly threaded hole in the cylinder head K. Beyond the screwthreaded part B2 is another cylindrical portion G of less diameter than the part i3l and terminating at a place which is near the end of the insulator wihin it. The extreme end portion of the plug cody is preferably formed conical as at H with an angle ot taper which may be about 30, the diameter ci the reduced end of this part being about one half of the diameter of the screwthreaded part This conical part H rests in a correspondingly conical seating K1 in the hole through the cylinder head and thus constitutes a gas seal.

The hexagonal formation J on the body, which is 'provided for engagement by a Spanner for inserting and removing the plug, is situated near the top A1 of the insulator. The distance between this hexagonal formation J and the remote end of the screwthreadedpart B2 of the body is conveniently not less than three times the length of the screwthreaded part B". Consequently the hole K2 in the cylinder head K for the insertion of the plug need only be of sumcient size to accommodate the cylindrical part Bl of the body and need not provide clearance for the hexagonal part and Ito allow for a spanner to engage it. Thus a smaller hole than usual can be employed and the hexagonal partis placed where it is more readily accessible.

The upper part of the body may be prolonged as at B3 to form an integral screen with the usual internal insulation K3, though if preferred the plug may be unscreened.

The invention is not limited to the details of construction described above by way of example, but is, for. instance, equally applicable to plugs of the type adapted to be taken apart.

What I claim as my invention and desire to secure by Letters Patent is:

1. A sparking plug comprising a metal body, an insulator within the body, and a gas-tight gland including a washer and a ring between the insulator and the body and through one of the parts of which heat from the insulator can flow to the body, the part of the body which lies around and adjacent to the gland ring having a uniform external diameter with a screwthread thereon which runs from the end of this part of uniform diameter towards a part which surrounds the gland.

2. A sparking plug comprising a metal body, an insulator within the body, and a gas-tight gland including a washer and a ring between the insulator and the body and through one of the parts of which heat fromp the insulator can how radially to the body, and a screwthread on the exterior of the body which runs for some distance over the part of the body which lies around at least some portion of the gland.

3. A sparking plug comprising a metal body, an insulator within the body, and a gas-tight gland including a washer and a ring between the insulator and the body and through one of the parts of which heat from the insulator can flow to the body, and having a screwthread on the exterior of the body which engages the screwthread in the hole in the cylinder head and by reason of the thread on the body lying at least in part around the gland ring in the plug provides a path along which heat can flow radially and substantially directly from the insulator through the gland ring to the body and thence to the cylinder head around the hole in which the plug is held by its threaded part.

4. A sparking plug for the cylinder head of an internal combustion engine the plug comprising a metal body, an insulator within the body, and a gas-tight gland including a washer and a ring between the insulator 'and the body and through one of the parts of which heat from the insulator can flow to the body, a part of the body having a uniform external diameter and this part extending over a greater portion of the length of the body than that portion which lies around the gland ring, a screwthread on the exterior of the uniform diameter part of the plug which thread is adapted to engage a threaded hole in the cylinder head, this screwthread running from substantially the inner end of the said body part of uniform diameter towards and over a part va, metal body, an insulator within the body, a gastight gland including a washer and a ring between the insulator and the body and through one of the parts of which heat from the insulator can ilcw tothe body, and a gas space between the inner end of the insulator which lies beyond the said gland and the inner end portion of the body, a part of the body having a uniform external diameter and this part extending from a place on that inner portion of the body which encloses the said gas space to a place on the outer part of the body which lies beyond that around the gland, a screwthread on the exterior of the uniform diameter part of the plug which thread is adapted to engage a threaded hole in the cylinder head, said screwthread running from the inner end of the said body part of uniform diameter which lies around the said gas space towards a part surrounding a portion of the gland thus providing a path along which heat can ow radially and substantially directly from the insulator through the gland ring and thence to the cylinder head.

. 6. A sparking plug comprising the features as set out in claim 5 and in which beyond the screwthreaded inner end portion of the body which en gages the threaded hole in the cylinder head there is a part of the body which is cylindrical and has a diameter substantially less than the diameter of the adjacent threaded and unthreaded part of the body which is of uniform diameter.

7. A sparking plug for the cylinder head of an internal combustion engine the plug comprising a metal body, an insulator within the body, and a gas-tight gland including a washer and a ring between the insulator and the body and through one of the parts of which heat from the insulator can flow to the body, a part of the body having a uniform external diameter and this part extending over a greater portion of the length of the body than that portion which lies around the gland, a screwthread on the exterior of the unii form diameter part of the plug which thread is adapted to engage a threaded hole in the cylinder head, said screwthread running from the inner end of the said body part of uniform diameter to and over a part which surrounds at least some portion of the gland thus providing a path along which heat can ow radially and substantially directly from the insulator through the gland ring to the body and thence to the cylinder head, the portion of the body beyond the screwthreaded part which engages the threaded hole in the cylinder head having a. diameter substantially less than the said part of uniform diameter and ending in a conical part which engages a corresponding conical seat in the hole in the cylinder head.

8. A sparking plug comprising the features as set out in claim '7 in which at the outer end of the part of the body which externally is of uniform diameter and remote from the screwthreaded end piortion there isv externally a hexagonal format on.

9. A sparmng plug for the cylinder head of an internal combustion engine the plug comprising a metal body, an insulator within the body, a gastight gland including a washer and a ring between the insulator and the body and through one oi' the parts of which heat from the insulator can flow to the body, and a gas space between the inner end of the insulator which lies beyond the said gland and the end portion of the body, a part of the body having a uniform external diameter and separated from the upper part oi the insulator to provide a second gas space, this part being of uniform diameter and extending from a place on that portion of the body which encloses the second gas space to a piace on the outer part loi the body which lies beyond that around the gland ring, a screwthread on the exterior of the uniform diameter part of the plug which thread is adapted to engage a threaded hole in the cylinder head, said screwthread running from the inner end of the said body part of 

